1. Field of the Invention
The present invention relates to a liquid-drop discharge device used in various machineries for processing liquid by performing discharge of liquid.
2. Description of the Prior Art
Ink jet discharge devices as disclosed, for instance, in Japanese Patent Unexamined Publication No. 6-40030 (1994) are conventionally known types of devices for discharging liquid in form of minute particles used in particular fields. However, such discharge devices are used in offices or schools under relatively stationary conditions with little fluctuations in temperature or pressure of peripheral environments when being used, and are not exposed to significant fluctuations in operating environments.
On the other hand, minute powders of various chemicals are being used as auxiliary products for manufacturing semiconductors or the like, wherein the required standards in view of particle size can not be achieved by simply using mechanical crushing means, and developments in manufacturing methods of new types of powder are desired. It is urgently necessary to employ, as one exemplary method, a method for supplying raw materials in forms of minute particles to reaction cells such as drying chambers in a stable manner. Thus, devices that may be used with such methods for dropping liquid as particles from several hundredths of a nanometer to several tenths of a micron in a stable and controlled manner are needed.
While remarkable fluctuations in environments of discharge spaces are likely to occur at the time of operating such devices, due to fluctuations in operating conditions or the like, it is presently the case that no device has yet been proposed with which liquid can be supplied as minute particles in a desirable manner even though in the presence of fluctuations in discharge spaces.
The present invention has been made to provide a liquid discharge device for raw materials, or the like, of an arrangement that is capable of continuously adjusting conditions for discharging liquid to be an optimal condition in accordance with fluctuating peripheral environments, even when an environment of discharge space radically and abruptly fluctuates, or air bubbles are present. Further, a liquid discharge device that is capable of steadily discharging liquid regardless of the size of the operating range is desired.
For solving the above objects, the inventors of the present invention have devised an invention that is related to a liquid-drop discharge device comprising a liquid storage tank, a liquid discharge means for discharging liquid within the liquid storage tank, and a reaction cell provided with a space into which liquid is discharged from the liquid discharge means. The liquid discharge means comprises a discharge outlet provided at an end portion of a flow path opening to the reaction cell, an opening degree means for adjusting an opening degree of the discharge outlet, and an oscillating means for applying oscillation to liquid introduced into the flow path. Accordingly, a flow of liquid that has been oscillated by the oscillating means is sucked and atomized from an air-contacting surface of the discharge outlet by an internal pressure of the reaction cell when P1xe2x89xa7P3, which is satisfied when the internal pressure of the liquid storage tank and the internal pressure of the reaction cell are respectively defined as P1 and P3.
With this arrangement, liquid may be discharged in a steady and well-controlled manner despite the presence of air bubbles in liquid within the flow path, wherein the flow of liquid applied with minute oscillation by the oscillating means is atomized, and atomization caused through suction of the air-contacting surface of the discharge outlet by the internal pressure of the reaction cell may be continued while maintaining a minute spraying condition. When the internal pressure of the liquid storage tank and the internal pressure of the reaction cell are identical, spraying of a small amount may be performed even through fibrillation of the oscillating means, so that it is possible to cope with various amounts of spraying of a wide range from a large capacity to a small amount.
It should be noted that as an exemplary means for setting the internal pressure P3 of the reaction cell to be not more than the internal pressure P1 of the liquid storage tank, air is supplied to the reaction cell, and if necessary, a negative pressure may be effectively achieved by narrowing a sectional surface area of a portion of the reaction cell that is open to the discharge outlet in contrast to other portions.
The present invention further relates to a liquid-drop discharge device wherein the liquid discharge means comprises a discharge outlet provided at an end of a flow path opening to the reaction cell, and an oscillating means concurrently provided with a function of adjusting an opening degree of the discharge outlet and of applying fibrillation to liquid introduced into the flow path through the discharge outlet. With this arrangement, it is possible to simplify arrangements of driving portions and to decrease manufacturing costs for performing atomization in an effective manner.
It should be noted that the concurrently used oscillating means may be arranged by employing a method in which instructions for adjusting opening degrees are issued at the time of starting operation, instructions for applying minute oscillation are repetitively issued in a single structure, or a method in which a structure for adjusting the opening degree and a structure for applying minute oscillation are laminated and provided at an end of the flow path.
The opening degree means may be arranged in a valve arrangement, in which a valve body provided at a thin film portion of a wall portion of a flow path end portion is arranged adjacent to a seat opening to the reaction cell for varying an inner diameter of the flow path, wherein a projecting member formed inside of the flow path for narrowing the inner diameter of the flow path may be provided either at the valve seat or the valve body. A pressurizing member provided outside of the thin film portion of the wall portion of the flow path end portion may be comprised by a laminated actuator, a thin film actuator with a comb-like electrode arrangement of a style in which piezoelectric bodies are arranged between cathode and anode comb-teeth or in which the piezoelectric bodies are arranged to be parallel with respect to the cathode and anode comb-like arrangement, or a solenoid coil.
It is particularly preferable that the liquid discharge means be comprised of a flow path having a wall surface with at least one surface thereof being arranged to be thinner than the remaining surfaces. It is also preferable that the opening degree means be arranged in that the sectional surface area of the flow path is varied by utilizing distortion of a piezoelectric/electrostrictive element provided at least at one portion of the thin wall portion of the flow path end portion.
With this arrangement, it is possible to perform discharge at low electric consumption and in a well-controlled manner, and to further decrease manufacturing costs. When the opening degree means is concurrently provided as the oscillating means, it is favorably possible to perform high-frequency oscillation and to perform rapid adjustment of the opening degree. In order to enable large displacements of the thin film portion of the wall portion of the flow path for adjusting the opening degree, it is possible to form the end portion of the flow path to be wide in a direction orthogonal to a direction of displacement and to provide the discharge outlet in a center thereof as the end portion of the flow path.
The oscillating means may be comprised of a laminated actuator or a thin film actuator, which is arranged to pinch piezoelectric bodies between cathodes and anodes, outside of the thin film portion of the wall portion of the flow path. It is particularly preferable that the liquid discharge means be comprised of a flow path having a wall surface with at least one surface thereof being arranged to be thinner than remaining surfaces, and that the oscillating means be arranged to apply minute oscillation to liquid by utilizing distortion of a piezoelectric/electrostrictive element provided at least at one portion of the thin wall portion of the flow path. With this arrangement, it is not only possible to provide an oscillating means of large amplitude at low costs, but also to perform high-frequency driving at low voltage.
The oscillating means provided outside of the thin film portion of the wall portion may be disposed to surround the discharge outlet in which a piercing hole for the opening degree means is provided at a center thereof to extend along an outer periphery of the discharge outlet, or a rectangular oscillating member may be disposed proximate to the discharge outlet. Either one or a plurality of rectangular oscillating members may be provided at this time, and when a plurality thereof are provided, they may be disposed around the discharge outlet in a radial manner. For transmitting oscillation to liquid in an effective manner, the oscillating means may be formed at more upper thin wall portions when compared to the opening degree means, and oscillating members located remote from the discharge outlet may be disposed to be oblique with respect to the wall surface, for making directions of amplitude face the discharge outlet such that oscillation may be focused at the discharge outlet.
It is preferable that the discharge outlet be arranged in that its portion opening to the reaction cell is formed to assume a shape of an elongated hole for increasing a surface area of discharge and an amount of spraying. It is also preferable to dispose a float cell that is connected to between the liquid storage tank and the liquid discharge means with a check valve being formed at the liquid storage tank for functioning to maintain a constant liquid surface with a constant capacity. The back pressure of the liquid from the liquid storage tank may thus be made constant and leakage of liquid from the discharge outlet upon being pressurized may be prevented.